Luminescent panel having a reflecting film to reflect light outwardly which is shaped to condense the reflected light

ABSTRACT

A luminescent panel includes a transparent substrate, a first transparent electrode provided on the transparent substrate, a luminescent layer provided on the first transparent electrode, and a second transparent electrode provided on the luminescent layer. A reflecting film provided on the second electrode, reflects light emitted from the luminescent layer through the second transparent electrode and causes the reflected light to outwardly emit from the transparent substrate.

This application is a U.S. National Phase Application under 35 USC 371of International Application PCT/JP03/05998 filed May. 14, 2003.

TECHNICAL FIELD

The present invention relates to a luminescent panel including anoptical member which improves an emitting efficiency.

BACKGROUND ART

Generally, since an EL element is a self-luminous type element, it isused as a backlight in a liquid crystal display, a light source in aprinter head, a segment in a segment type display, a pixel in a matrixtype display and others. In particular, a display in which the ELelement functions as a pixel achieves a wide field angle, high contrast,an excellent visual recognition property, a low power consumption, agood shock resistance and others. As the EL elements, there are aninorganic EL element which is a thin film structure in which insulatingfilms are interposed between an EL layer using an inorganic compound asa luminescent material and a pair of electrodes, and an organic ELelement which is a laminated structure using an organic compound as aluminescent material.

FIG. 22 shows a structure of a typical luminescent panel using organicEL elements. A luminescent panel 901 is constituted by sequentiallylaminating an anode electrode 903, an organic EL layer 904 including aluminescent material and a cathode electrode 905 on one surface 902a ofa transparent substrate 902. The organic EL layer 904 may have athree-layer structure including a hole transport layer, a luminescentlayer and an electron transport layer laminated on the cathode electrode903 in the mentioned order, a two-layer structure consisting of anelectron hole transport layer and a luminescent layer from the side ofthe anode electrode 903 in the mentioned order, a single-layer structureconsisting of a luminescent layer, or a laminated structure thattransport of electrons or electron holes is interposed betweenappropriate layers in the former layer structures.

In the luminescent panel 901, when a forward bias voltage is appliedbetween the anode electrode 903 and the cathode electrode 905, theelectron holes are injected into the organic EL layer 904 from the anodeelectrode 903, and the electrons are injected into the organic EL layer904 from the cathode electrode 905. When the electron holes and theelectrons are transported into the organic EL layer 904 and the electronholes and the electrons are re-combined in the organic EL layer 904,excitons are generated, and a fluorescent material in the organic ELlayer 904 is excited by the excitons whereby light is generated in theorganic EL layer 904.

Generally, the luminescent panel 901 uses the anode electrode 903 as atransparent electrode, and the light is emitted toward the outside fromthe other surface 902 b of the transparent substrate 902. At thismoment, since the light emitted from the organic EL layer 904 spreads ina radial pattern, the light emitting efficiency is improved in theluminescent panel 901 by providing the light blocking effect to thecathode electrode 905.

Since the light does not have the directivity in the luminescent panel901 and the light emitted from the organic EL layer 904 spreads in aradial pattern, a part of the light passing through the transparentsubstrate 902 is scattered in the transparent substrate 902, therebyreducing the light emitting efficiency from the transparent substrate902 to the outside.

Further, when the luminescent panel 901 is used in a matrix typedisplay, since the light emitted from the organic EL layer 904 spreadsin a radial pattern, it is hard to sufficiently increase the contrast ofa display screen in the front face direction.

Thus, the present invention is advantageous in increasing the lightemitting efficiency of the light emission panel by a light emissionelement such as an organic EL element forming a laminated structurelaminated on a transparent substrate and providing the directivity tolight emission of a luminescent panel.

DISCLOSURE OF INVENTION

According to one aspect of the present invention, there is provided aluminescent panel comprising:

-   -   a transparent substrate;    -   a first transparent electrode provided on one surface of the        transparent substrate;    -   a luminescent layer provided on the first transparent electrode;    -   a second transparent electrode provided on the to luminescent        layer, at least one pixel being defined by the first transparent        electrode, the luminescent layer and the second transparent        electrode; and    -   a reflecting film which reflects light radiated from the        luminescent layer through the second transparent electrode and        causes the reflected light to outgo from the transparent        substrate.

In this luminescent panel, when the luminescent layer emits the light, apart of the light is transmitted through the first electrode and thetransparent substrate as it is and outgoes from the other surface of thetransparent substrate. On the other hand, the remaining part of thelight is transmitted through the second electrode and then reflected onthe reflecting film. The reflected light is transmitted through thesecond electrode, the luminescent layer, the first electrode and thetransparent substrate, and outgoes from the other surface of thetransparent substrate. Here, the reflecting film need not closelycontact the luminescent layer as the second electrode. That is, when theluminescent layer is flat, the second electrode film must be also formedflatly, whereas the reflecting film can be set to an arbitrary shapeirrespective of the shape of the luminescent layer. Therefore, since thereflecting film can arbitrarily control the reflected light, theemitting efficiency of the light from the transparent substrate side canbe improved.

The reflecting film functions as a concave mirror when it is formed tohave a concave portion, and the front face brightness can be improved inparticular. Also, it is possible to perform display with the extremelyhigh contrast ratio with respect to a viewer from the front side. Inparticular, when this luminescent panel is used as a personal smallpanel, visual recognition is performed almost only from the front side,which is very effective. Further, in order to readily define the shapeof the reflecting film, a lens may be provided on the inner side or theouter side of the reflecting film.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1A is a cross-sectional view showing a part of a luminescent panelaccording to a first embodiment of the present invention, and FIG. 1B isa graph showing a luminescent characteristic of this luminescent panel;

FIG. 2 is a cross-sectional view showing a part of the luminescent panelincluding a switching element;

FIG. 3A is a cross-sectional view showing a part of a luminescent panelaccording to a second embodiment, and FIG. 3B is a graph showing aluminescent characteristic of this luminescent panel;

FIG. 4A is a cross-sectional view showing a part of a luminescent panelaccording to a third embodiment, and FIG. 4B is a graph showing aluminescent characteristic of this luminescent panel;

FIG. 5A is a cross-sectional view showing a part of a luminescent panelaccording to a fourth embodiment, and FIG. 5B is a graph showing aluminescent characteristic of this luminescent panel;

FIG. 6A is a cross-sectional view showing a part of a luminescent panelaccording to a fifth embodiment, and FIG. 6B is a graph showing aluminescent characteristic of this luminescent panel;

FIG. 7A is a cross-sectional view showing a part of a luminescent panelaccording to a sixth embodiment, and FIG. 7B is a graph showing aluminescent characteristic of this luminescent panel;

FIG. 8A is a cross-sectional view showing a part of a luminescent panelaccording to a seventh embodiment, and FIG. 8B is a graph showing aluminescent characteristic of this luminescent panel;

FIG. 9A is a cross-sectional view showing a part of a luminescent panelof an eighth embodiment, and FIG. 9B is a graph showing a luminescentcharacteristic of this luminescent panel;

FIG. 10A is a cross-sectional view showing a part of a luminescent panelof a ninth embodiment, and FIG. 10B is a graph showing a luminescentcharacteristic of this luminescent panel;

FIG. 11A is a cross-sectional view showing a part of a luminescent panelaccording to a tenth embodiment, and FIG. 11B is a graph showing aluminescent characteristic of this luminescent panel;

FIG. 12A is a cross-sectional view showing a part of a luminescent panelaccording to an eleventh embodiment, and FIG. 12B is a graph showing aluminescent characteristic of this luminescent panel;

FIG. 13A is a cross-sectional view showing a part of a luminescent panelaccording to a twelfth embodiment, and FIG. 13B is a graph showing aluminescent characteristic of this luminescent panel;

FIG. 14A is a cross-sectional view showing a part of a luminescent panelaccording to a thirteenth embodiment, and FIG. 14B is a graph showing aluminescent characteristic of this luminescent panel;

FIG. 15 is a cross-sectional view showing a part of a luminescent panelaccording to a fourteenth embodiment;

FIG. 16 is a cross-sectional view showing a part of a luminescent panelaccording to a fifteenth embodiment;

FIG. 17 is a cross-sectional view showing a part of a luminescent panelaccording to a sixteenth embodiment;

FIG. 18 is a cross-sectional view showing a part of a luminescent panelaccording to a seventeen embodiment;

FIG. 19 is a cross-sectional view showing a part of a luminescent panelaccording to an eighteen embodiment;

FIG. 20 is a cross-sectional view showing a part of a luminescent panelaccording to a nineteenth embodiment;

FIG. 21 is a cross-sectional view showing a part of a luminescent panelaccording to a twenty embodiment; and

FIG. 22 is a cross-sectional view showing a part of a luminescent panelaccording to a twenty-first embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Concrete modes of the present invention will now be describedhereinafter with reference to the accompanying drawings. However, ascope of the present invention is not restricted to illustratedembodiment. It is to be noted that, in the embodiments, “seen from aplane surface” means “seen from a direction of a substantial normal lineof a light emitting surface 2 b of a transparent substrate 2”.

FIG. 1A is a cross-sectional view showing a part of a luminescent panelto which the present invention is applied.

This luminescent panel 1 has as a basic structure a laminated structurein which an anode electrode 3, an organic EL layer 4 (luminescent layerin the broad sense) and a cathode electrode 5 are sequentially laminatedon one flat surface 2 a of a transparent substrate 2 having asubstantially tabular shape in the mentioned order. The anode electrode3 is constituted by many anode electrode sections or stripes which areseparated from each other at predetermined intervals, provided toprotrude from one surface of the organic EL layer 4 and extend in a rowdirection. A plurality of positions where each section of the anodeelectrode 3 and the cathode electrode 5 cross each other with theorganic EL layer 4 therebetween are defined as respective pixels, andeach pixel selectively emits the light in accordance with a voltage or acurrent applied to the anode electrode 3 and the cathode electrode 5.

The transparent substrate 2 has a refraction factor of 1.3 to 1.6, athickness of 0.1 mm to 1.3 mm, the transmissivity with respect to thevisible light and the insulation property, and it is formed of amaterial such as borosilicate glass, quartz glass or any other glass.

The film of the anode electrode 3 is formed on one surface 2 a of thetransparent substrate 2. The anode electrode 3 has the conductivity andthe transmissivity with respect to the visible light. Furthermore, asthe anode electrode 3, one which can efficiently inject electron holesto the organic EL layer 4 is preferable. The anode electrode 3 is formedof, e.g., an indiumtin-oxide (ITO), a zinc-doped indium oxide (In—Zn—O),an indium oxide (In₂O₃), a tin oxide (SnO₂), a zinc oxide (ZnO) or thelike, has a refraction index of approximately 2.0 to 2.2 and a thicknessof 50 nm to 200 nm.

The organic EL layer 4 is formed with a thickness of 20 nm to 200 nm onthe anode electrode 3. The organic EL layer 4 may include various chargetransport layers. For example, the organic EL layer 4 may have athree-layer structure having an electron hole transport layer, anarrow-sense luminescent layer, and an electron transport layersuperimposed on the anode electrode 3 in the mentioned order, or atwo-layer structure having an electron holes transport layer and aluminescent layer in a narrow sense superimposed on the anode electrode3, or a structure having one layer consisting of a narrow-senseluminescent layer, four or more layers, or a structure having anelectron transport layer or an electron transport layer interposedbetween appropriate layers in such layer structures, or any otherstructure. A refraction factor of the organic EL layer 4 isapproximately 1.3 to 1.6.

The organic EL layer 4 has a function to transport electron holes andelectrons and a function to generate excitons by re-coupling of theelectron holes and the electrons and emit the light. It is desirablethat the organic EL layer 4 is an organic chemical compound which iselectronically neutral, and the electron holes and the electrons arethereby injected and transported in the organic EL layer 4 in thewell-balanced manner. Further, a material having an electron transportproperty may be appropriately mixed in the narrow-source luminescentlayer, a material having an electron hole transport property may beappropriately mixed in the narrow-source luminescent layer, or amaterial having an electron transport property and a material having anelectron transport property may be appropriately mixed in thenarrow-source luminescent layer. A luminescent material (fluorescentmaterial) is included in the organic EL layer 4. This luminescentmaterial may be a high-molecular-based material or a low-molecular-basedmaterial.

The film of the cathode electrode 5 is formed on the organic EL layer 4.The cathode electrode 5 has a transmissivity with respect to the visiblelight. Furthermore, it is desirable that the cathode electrode 5 isformed of a material with a relatively low work function in light of anelectron injection property. As the cathode electrode 5, it is desirableto adopt one which has a laminated structure that the film of theelectron injection layer constituted by an elemental substance with alow work function, e.g., indium, magnesium, calcium, lithium or barium,or an alloy or a mixture including at least one kind of these materialsis formed with a thickness of approximately 2 nm to 15 nm on the organicEL layer 4 and the film of the high-transmissivity layer such as ITO isformed with a thickness of 50 nm to 200 nm on the electron injectionlayer, and the laminated structure of which transmits therethrough notmore than 70% of the visible light.

A lens array (fly-eye lens or fly-eye lenses) 7 having a plurality ofminute convex lenses aligned therein in the matrix form is bonded to thecathode electrode 5 by an optical adhesive 6. The optical adhesive 6 hasa transmissivity with respect to the visible light, and a refractionfactor approximating a refraction factor of the high-transmissivitylayer of the cathode electrode 5 or a refraction factor of the lensarray 7. In this embodiment, although Canada balsam is used as theoptical adhesive 6, the optical adhesive is not restricted to Canadabalsam.

The lens array 7 has a flat surface 7 a which is bonded to the cathodeelectrode 5. On the other surface 7 b of the lens array 7 are arranged aplurality of convex lenses 7 c in the matrix form with a pitch of 1 μmto 200 μm, or more desirably 25 μm to 75 μm when seen from the planesurface. Each convex lens 7 c has such a shape as that a bottom surfaceof a circular cone 7 e is superimposed on an upper surface of atruncated cone 7 d, a ratio of a height 2 x of the truncated cone 7 dand a height x of the circular cone 7 e is 2:1, and a ratio of a radius3 x of the bottom surface of the truncated cone 7 d and a radius 2 x ofthe bottom surface of the circular cone 7 e is 3:2. Therefore, an apexangle α of the circular cone 7 e is set to 120°.

A reflecting film 8 is formed on an irregular surface or concave/convexsurface 7 b of the lens array 7. The reflecting film 8 has areflectivity with respect to the visible light. As a material of thereflecting film 8, there may be used aluminium, silver and an alloy ofthese materials, but the material of the reflecting film 8 does not haveto be restricted them as long as the irregular surface 7 b of the lensarray 7 is a mirror finished surface and can reflect the visible light.As a method of forming the reflecting film 8, there are a sputteringmethod, a vapor deposition method and others, it is not necessary torestrict it to them.

Since the convex lens 7 c has a concave shape protruding in a directionopposite to a direction toward the transparent substrate 2, one convexlens 7 c and a part of the reflecting film 8 form one concave mirrorwhen viewing the lens array 7 from the transparent substrate 2. Thisconcave mirror faces the cathode electrode 5, and the cathode electrode5 is interposed between the concave mirror and the anode electrode 3.

As a method of manufacturing the luminescent panel 1 having theabove-described structure, the film of the anode electrode 3 is firstformed on the flat surface 2 a of the transparent substrate 2, and thefilm of the organic EL layer 4 is formed on the anode electrode 3. Then,the film of the cathode electrode 5 is formed on the organic EL layer 4.On the other hand, the film of the reflecting film 8 is formed on theirregular surface 7 b of the lens array 7. Then, the optical adhesive 6is applied on at least one of the cathode electrode 5 on the transparentsubstrate 2 side and the flat surface 7 a of the lens array 7, and theoptical adhesive 6 is used to bond the flat surface 7 a of the lensarray 7 to the cathode electrode 5. The optical adhesive 6 is cured,thereby bringing the luminescent panel 1 to completion.

In case of using the luminescent panel 1 as a display panel of an activematrix display type display, as shown in FIG. 2, it is good enough topartition the anode electrode 3 and the organic EL layer 4 in the matrixform when seen from the plane surface (that is, it is good to define aplurality of rectangular anode electrode sections and organic ELsections distanced from each other in the line direction and the rowdirection). In this case, the anode electrode sections and the organicEL layer sections are partitioned by an insulative partition wall 9formed in the mesh form or a plurality of walls when seen from the planesurface, the cathode electrode 5 which can function as a commonelectrode is arranged so as to cover the organic EL layers 4 and thepartition wall 9. In the organic EL element which becomes each pixel inthis manner, a luminescent area is partitioned by each section of theanode electrode 3 partitioned by the partition wall 9, and a transistorTr provided in the partition wall 9 is connected as a switching elementto each section of the anode electrode 3. One or more transistors Tr areprovided in accordance with each pixel. An a-Si/TFT or p-Si/TFT ispreferable as the transistor. A capacitor connected to-the transistor Trmay be provided for each pixel according to needs.

Each convex lens 7 c is arranged in accordance with each pixel (organicEL element), and one concave mirror constituted by one convex lens 7 cand a part of the reflecting film 8 faces each organic EL layer 4 of theorganic EL element. It is to be noted that the cathode electrode 5 ofeach organic EL element is determined as an electrode common to all thepixels, but the electrode connected to the transistor Tr may bedetermined as a cathode electrode whose side close to the transparentsubstrate 2 is patterned in accordance with each pixel with respect tothe organic EL layer 4, and the anode electrode may be determined as onecommon electrode so as to cover the partition wall 9 and the organic ELlayer 4. At this moment, when the cathode electrode is configured tohave an electron injection layer and a high-transmissivity layer asdescribed above, providing the electron injection layer on the organicEL layer 4 side can suffice.

Moreover, in case of a simple matrix, between a plurality of thepartition walls 9 arranged so as to be separated from each other by apredetermined distance along the line direction when seen from the planesurface may be arranged each anode electrode 3 likewise provided alongthe line direction, and the organic EL layer 4 is formed on the surfaceof the anode electrode 3. Thereafter, a plurality of the cathodeelectrodes 5 separated from each other by a predetermined distance maybe formed on the surface of the organic EL layer 4 along the rowdirection orthogonal to the line direction.

When a step is generated in the plane direction by the transistor Tr andthe partition walls 9 or the anode electrode 3 and the organic EL layer4, since the optical adhesive 6 having the flexibility when unhardenedis interposed in a gap produced in the irregularities so as to cancelout the irregularities, the lens array 7 can be stably bonded to thetransparent substrate 2 in parallel.

As a method of manufacturing the luminescent panel 1 shown in FIG. 2, aplurality of the anode electrodes 3 are patterned in the matrix form onthe flat surface 2 a of the transparent substrate 2 by appropriatelyperforming a thin film formation step such as a vapor evaporationmethod, a sputtering method or a CVD method, a masking step such as aphotolithography method, or the thin film shape manufacturing step suchas an etching method. Then, wirings connecting the transistors Tr and adrive circuit which controls, the transistors Tr and the pixels areformed between a plurality of the anode electrodes 3 on the transparentsubstrate 2.

Subsequently, each partition wall 9 is formed on the transistor Tr andthe wiring by the photolithography method. That is, a resist film(photosensitive polyimide film) is formed on the flat surface 2 a of thetransparent substrate 2, the part of the resist film which can be thepartition wall 9 is exposed (that is, the part superimposed on the anodeelectrode 3 is exposed), and a part other than the exposed part of theresist film is eliminated by a developer. As a result, shaping of theresist film is performed so that the remaining part of the resist filmbecomes the partition wall 9.

Thereafter, a high-molecular material including a luminescent materialis solved by a solvent, and the solvent is caused to belch out asdroplets to each surrounded area surrounded by the partition wall 9.Then, the droplet spreads on the anode electrode 3 and becomes a film.When this film-is hardened, the organic EL layer 4 is formed.

Subsequently, the cathode electrode 5 is formed by the film forming stepsuch as a vapor deposition method, a sputtering method or a CVD method.Although the number of the cathode electrode 5 shown in FIG. 2 is one, aplurality of the cathode electrodes 5 arranged in the matrix form may beused in some cases. In such a case, after forming the film of aconductive film which can be the cathode electrode, a plurality ofcathode electrodes 5 arranged in the matrix shape are formed byperforming the masking step such as a photolithography method or thethin film shape manufacturing step such as an etching method.

The reflecting film 8 is formed on the irregular surface 7 b of the lensarray 7. Then, the optical adhesive 6 is applied to at least one of thecathode electrode 5 on the transparent substrate 2 side and the flatsurface 7 a of the lens array 7, and the optical adhesive 6 is used tobond the flat-surface 7 a of the 2 b lens array 7 to the cathodeelectrode 5. At this moment, positioning is performed in such a mannerthat each convex lens 7 c is superimposed on each cathode electrode 5when seen from the plane surface, and the lens array 7 is bonded to thecathode electrodes 5. Then, the optical adhesive 6 is hardened, therebybringing the luminescent panel 1 shown in FIG. 2 to completion.

In the luminescent panel 1 shown in FIG. 1A or FIG. 2, when the forwardbias voltage (the potential of the anode electrode 3 is higher than thepotential of the cathode electrode 5) is applied between the anodeelectrode 3 and the cathode electrode 5, the electron holes are injectedinto the organic EL layer 4 from the anode electrode 3, and theelectrons are injected from the cathode electrode 5 into the organic ELlayer 4. Then, the electron holes and the electrons are transported tothe narrow-sense luminescent layer of the organic EL layer 4, and theelectron holes and the electrons are re-coupled in the narrow-senseluminescent layer, thereby generating the excitons. The excitons excitethe fluorescent material in the organic EL layer 4 to emit the light.Since the anode electrode 3 and the substrate 2 are transparent withrespect to the luminescent wavelength band of the organic EL layer 4, apart of the light emitted in the organic EL layer 4 passes through theanode 3 and the transparent substrate 2, and outgoes from the flat lightemitting surface 2 b of the transparent substrate 2. Since the cathodeelectrode 5, the optical adhesive 6 and the lens array 7 are alsotransparent with respect to the luminescent wavelength band of theorganic EL layer 4, the remaining part of the light from the organic ELlayer 4 is reflected on the reflecting film 8 through the cathodeelectrode 5, the optical adhesive 6 and the lens array 7, and thereflected light passes through the lens array 7, the transparentadhesive 6, the cathode electrode 5, the organic EL layer 4, the anodeelectrode 3 and the transparent substrate 2, and outgoes from the lightemitting surface 2 b.

In the luminescent panel 1 shown in FIG. 1A or FIG. 2, since the concavemirror faces the cathode electrode 5, the light directed toward thereflecting film 8 from the organic EL layer 4 is reflected so as to becondensed at the central part. That is, the light directed toward thereflecting film 8 from the organic EL layer 4 passes the apex of theconvex lens 7 c and is reflected so as to be condensed or focused towardthe normal line direction of the light emitting surface 2 b. Therefore,the luminescent brightness of the luminescent panel 1 is very high whenseen from the normal line direction of the light emitting surface 2 b.Therefore, the light emitted from the organic EL layer 4 can beprevented from evenly spreading in the radial pattern on the lightemitting surface 2 b. In particular, when it is used for the matrixdisplay type display like the luminescent panel 1 shown in FIG. 2, sincethe light emitted from the organic EL layer 4 can be suppressed fromspreading in the radial pattern, it is not strongly diffused tosurrounding pixels, and display with the high contrast ratio can berealized.

A graph of FIG. 1B is a graph showing the directivity of the outgoinglight of the luminescent panel 1 shown in FIG. 1A, in which angles ofaxes radially extending from a starting point O in the light emittingsurface 2 b represent measured angles with respect to the light emittingsurface 2 b, and distances from the starting point O represent lightintensity ratios (ratios of the brightness [cd/m²]). The transparentsubstrate 2 is set to have a refraction factor of 1.5 and a thickness of0.7 mm. It is to be noted that the anode electrode 3, the organic ELlayer 4, the cathode electrode 5 and the optical adhesive 6 are verythin as compared with the transparent substrate 2. As refraction factorsof these members, it is desirable to adopt refraction factors which donot greatly affect the directivity of the light intensity ratio but arelow.

A line L901 represents a light intensity ratio of the luminescent panel901 of FIG. 22 (where the cathode electrode 905 has the reflectivitywith respect to the visible light). Providing that the light intensityratio is 1 when seen from the normal line direction, the light intensityratio of any angle is dimensionless.

A line L1 represents a light intensity ratio of the luminescent panel 1of FIG. 1A, and this is a relative value expressing the light intensityas 1 when viewing the luminescent panel 901 from the normal linedirection of the surface 902 b as a comparative example.

Various conditions in this embodiment (e.g., a film thickness of eachlayer, a material of each layer, a level of an application voltage, aluminescent area, a level of a passing current and others) are equal tothose in the prior art except that the lens array 7 and the reflectingfilm 8 are provided.

As shown in FIG. 1B, the brightness in the luminescent panel 1 accordingto this embodiment is substantially the same as the brightness in theprior art luminescent panel in the angle range of 0° to 60°. However, incase of an angle more than 60°, the brightness in the luminescent panel1 in this embodiment is higher than the brightness in the prior artluminescent panel. In particular, when the angle is not less than 80°, adifference in brightness is considerable.

As described above, since the luminescent panel 1 includes the concavemirror so as to be opposed to the transparent cathode electrode 5, theemitting efficiency is improved within 30° on the right and left sideswith respect to the light emitting surface 2 b. In particular, theemitting efficiency within 5° on the right and left sides is improved tobe double or more.

In addition, since the concave mirror is provided so as to be opposed tothe transparent cathode electrode 5, the brightness when seen from thenormal line direction with respect to the light emitting surface 2 bbecomes high without increasing the current or the voltage of theluminescent panel 1. In other words, since the luminescent brightnessbecomes high without increasing the level of the current flowing throughthe luminescent panel 1, the long duration of life and the low powerconsumption of the luminescent panel 1 can be realized, therebyimproving the light emitting efficiency of the luminescent panel 1.

When this luminescent panel 1 is used as the display panel of thedisplay, the brightness when seen from the normal line directionrelative to the light emitting surface 2 b is high, thereby providingthe display with the high contrast.

By appropriately changing the shape of the lens array, the shape of theconcave mirror can be appropriately varied as shown in FIGS. 3A, 4A, 5A,6A, 7A and 8A. In the luminescent panels 10 to 15 shown in FIGS. 3A, 4A,5A, 6A, 7A and 8A described below, like reference numerals denoteconstituent elements equal to those in the luminescent panel 1. In theseembodiments, the anode electrodes 3 are separated from each other in therow direction by a plurality of protrusions which are provided on onesurface of the organic EL layer 4 so as to protrude at predeterminedintervals in the row direction and extend in the column direction, andthe cathode electrodes 5 are separated from each other in the linedirection by a plurality of protrusions (not shown in the drawing) whichare provided on the other surface so as to protrude with predeterminedintervals in the column direction and extend in the row direction. Inthis manner, the separated anode electrode sections or first stripelectrodes cross the separated cathode electrode sections or secondstrip electrodes at many points, and these parts and the parts of theorganic EL layer sandwiched therebetween constitute pixels.

In the luminescent panel 10 shown in FIG. 3A, as to the shape of thelens array 71, its surface 71 a bonded to the cathode electrode 5 is aflat surface. Irregular surface 71 b on the opposite side has a shapethat a plurality of convex lenses 71 c are arranged in the matrix shapewhen seen from the plane surface. The convex lens 71 c has asubstantially circular cone shape. Forming the film of a reflecting film8 on the irregular surface 71 b forms concave mirrors consisting of theconvex lenses 71 c and the reflecting film 8. Additionally, two oppositeside lines which are in contact with an apex angle α are set to the samelength. In FIG. 3B, a line L10 represents a light intensity ratio of theluminescent panel 10 shown in FIG. 3A, and this is expressed as arelative value representing the light intensity as 1 when viewing theluminescent panel 901 from the normal line direction of the surface 902b. Here, there are illustrated cases where the apex angles α of theconvex lens 71 c are 90° and 100°. In any case, this panel is brighterover 180° than the luminescent panel 901. In particular,.the brightnesswhen seen from the normal line direction relative to the light emittingsurface 2 b is greatly high as compared with the prior art, and thistendency is more prominent when the apex angle α is 100° rather than90°.

In the luminescent panel 11 shown in FIG. 4A, as to the shape of thelens array 72, its surface 72 a bonded to the cathode electrode 5 is aflat surface. An irregular surface 72 b on the opposite side has a shapethat a plurality of convex lenses 72 c are arranged in the matrix shapewhen seen from the plane surface. The convex lens 72 c has a truncatedcone shape, and a ratio of a height x from a valley of the truncatedcone to a small upper surface and a diameter x of the small uppersurface is 1:1 whilst a ratio of a diameter 3 x of a large bottomsurface of the truncated cone (distance between valleys) and a width xof the small upper surface is 3:1. The reflecting film 8 is formed onthe irregular surface 72 b, so that concave mirrors consisting of theconvex lenses 72 c and the reflecting film 8 are formed. In FIG. 4B, aline L11 represents a light intensity ratio of the luminescent panel 11of FIG. 4A, and this is expressed as a relative value representing thelight intensity as 1 when viewing the luminescent panel 901 from thenormal line direction of the surface 902 b as a comparative example. Theluminescent panel 11 is brighter over approximately 180° than theluminescent panel 901. In particular, it demonstrates the brightnessequal to or above the front face brightness of he luminescent panel 901over approximately 40° on the right and left sides relative to thenormal line direction of the light emitting surface 2 b.

In the luminescent panel 12 shown in FIG. 5A, as to the shape of thelens array 73, its surface 73 a bonded to the cathode electrode 5 is aflat surface. Its irregular surface 73 b on the opposite side has ashape that a plurality of convex lenses 73 c are arranged in the matrixfrom when seen from the plane surface. The convex lens 73 c has atruncated cone shape, and a ratio of a height x of the truncated coneand a diameter 4 x of a small upper surface is 1:4 whilst a ratio of adiameter 6 x of a large bottom surface of the truncated cone and a width4 x of the small upper surface is 6:4. Forming the reflecting film 8 onthe irregular surface 73 b constitutes a concave mirrors consisting ofthe convex lenses 73 c and the reflecting film 8. In FIG. 5B, a line L12represents a light intensity ratio of the luminescent panel 12 shown inFIG. 5A, and this is expressed as a relative value representing thelight intensity as 1 when viewing the luminescent panel 901 from thenormal line direction of the surface 902 b as a comparative example. Theluminescent panel 12 is brighter over approximately 180° than theluminescent panel 901. In particular, it demonstrates the brightnessequal to or above the front face brightness of the luminescent panel 901over approximately 40° on the right and left sides with respect to thenormal line direction of the light emitting surface 2 b.

In the luminescent panel 13 shown in FIG. 6A, as to the shape of thelens array 74, its surface 74 a bonded to the cathode electrode 5 is aflat surface. Its irregular surface 74 b on the opposite side has ashape that a plurality of convex lenses 74 c are arranged in the matrixform when seen from the flat surface. The convex lens 74 c has a curvedsurface and a semispherical shape that a height of the convex portion isx with respect to a distance 2 x between concave portions of the convexlens 74 c. The reflecting film 8 is formed on the irregular surface 74b, so that concave mirrors consisting of the convex lenses 74 c and thereflecting film 8 are formed. In FIG. 6B, a line L13 represents a lightintensity of the luminescent panel 13 shown in FIG. 6A, and this isexpressed as a relative value representing the light intensity as 1 whenviewing the luminescent panel 901 from the normal line direction of thesurface 902 b. The luminescent panel 13 is brighter than the luminescentpanel 901 over approximately 40° on the right and left sides of thenormal line direction of the light emitting surface 2 b.

In the luminescent panel 14 shown in FIG. 7A, as to the shape of thelens array 75, its surface 75 a bonded to the cathode electrode 5 is aflat surface. Its irregular surface 75 b on the opposite side has ashape that a plurality of convex lenses 75 c are arranged in the matrixform when seen from the plane surface. A cross-sectional shape of theconvex lens 75 c is semioval, and a ratio of the major axis 3 x (widthof the bottom surface) and the minor axis 2 x (height) is 3:2. Thereflecting film 8 is formed on the irregular surface 75 b, so that anon-spherical concave mirrors consisting of the convex lenses 75 c andthe reflecting film 8 are formed. In FIG. 7B, a line L14 represents alight intensity ratio of the luminescent panel 14 shown in FIG. 7A, andthis is expressed as a relative value representing the light intensityas 1 when viewing the luminescent panel 901 from the normal linedirection of the surface 902 b as a comparative example. The luminescentpanel 14 is brighter than the luminescent panel 901 over approximately60° on the right and left sides with respect to the normal linedirection of the light emitting surface 2 b.

In the luminescent panel 15 of FIG. 8A, as to the shape of a lens array76, its surface 76 a bonded to the cathode electrode 5 is a flatsurface. Its irregular surface 76 b on the opposite side has a shapethat a plurality of convex lenses 76 c are arranged in the matrix formwhen seen from the plane surface. A cross-sectional shape of the convexlens 76 c is semioval, and a ratio of the minor axis (width of thebottom surface) and the major axis (height) is 2:3. The reflecting film8 is formed on the irregular surface 76 b, so that non-spherical concavemirrors consisting of the convex lenses 76 c and the reflecting film 8are formed. In FIG. 8B, a line L15 represents a light intensity of theluminescent panel 15 shown in FIG. 8A, and this is expressed as arelative value representing the light intensity as 1 when viewing theluminescent panel 901 from the normal line direction of the surface 902b as a comparative example. The luminescent panel 15 is brighter thanthe luminescent panel 901 over approximately 20° to 35° on the right andleft sides with respect to the normal line direction of the lightemitting surface 2 b.

In FIGS. 3A, 4A, 5A, 6A, 7A and 8A, the anode electrode 3, the organicEL layer 4 and the cathode electrode 5 may be partitioned by partitionwalls 9 in the matrix form seen from the plane surface as shown in FIG.2. In this case, one concave mirror constituted by one of the convexlenses 71 c to 76 c and the part of the reflecting film 8 faces onepartitioned area (the anode electrode 3, the organic EL layer 4 and thecathode electrode 5 are superimposed in this area).

In the luminescent panels 1, 10 to 12 shown in FIGS. 1A, 2, 3A, 4A and5A, a translucent lens array may be provided on one surface of thetransparent substrate 2.

FIG. 9A shows a luminescent panel 1′ in which the transparent substrate2 of the luminescent panel 1 shown in FIG. 1A is substituted by atransparent lens array substrate 21. The anode electrode 3, the organicEL layer 4 and the cathode electrode 5 are sequentially superimposed onthe flat surface 21 a of the lens array substrate 21. A corrugatedsurface 21 b of the lens array substrate 21 is a light emitting surface,and a plurality of convex lenses 21 c are arranged in the matrix form.The convex lens 21 c has a circular cone shape that two opposite sidelines which are in contact with an apex angle β in a cross section alongan apex have the same length y. When seen from the plane surface, eachconvex lens 21 c is superimposed on the convex lens 7 c in such a mannerthat an apex of each convex lens 21 c is opposed to the apex of theconvex lens 7 c. In FIG. 9B, a light L1′ represents a light intensityratio of the luminescent panel 1′ in FIG. 9A, and this is expressed as arelative value representing the light intensity as 1 when viewing theluminescent panel 901 from the normal line direction of the surface 902b as a comparative example. The luminescent panel 1′ is brighter thanthe luminescent panel 901 over approximately 180°. In particular, itdemonstrates the brightness equal to or above the front face brightnessof the luminescent panel 901 over approximately 60° on the right andleft sides from the front face direction of the lens-array substrate 21.

FIG. 10A shows a luminescent panel 10′ in which the transparentsubstrate 2 of the luminescent panel 10 shown in FIG. 3A is substitutedby a lens array substrate 21. The anode electrode 3, the organic ELlayer 4 and the cathode electrode 5 are sequentially laminated on theflat surface 21 a of the lens array substrate 21. The corrugated surface21 b of the lens array substrate 21 is a light emitting surface, and aplurality of convex lenses 21 c are arranged in the matrix form. Theconvex lens 21 c has the same circular cone shape as that shown in FIG.9A. Further, each convex lens 21 c is superimposed on the convex lens 71c in such a manner that the apex of each convex lens 21 c is opposed tothe apex of the convex lens 71 c when seen from the plane surface. InFIG. 10B, a line L10′ represents a light intensity ratio of theluminescent panel 10′ shown in FIG. 10A, and this is expressed as arelative value representing the light intensity as 1 when viewing theluminescent panel 901 from the normal line direction of the surface 902b as a comparative example. Here, there are illustrated a case that anapex angle β of the convex lens 21 c and an apex angle α of the convexlens 71 c are 900 and a case that the apex angle β of the convex lens 21c and the apex angle α of the convex lens 71 c are 1000. The luminescentpanel 10′ is brighter than the luminescent panel 901 over approximately180° even if the both apex angles α and β are 90° or 100°. Inparticular, it demonstrates the brightness equal to or above the frontface brightness of the luminescent panel 901 over approximately 40° onthe right and left sides from the front face direction of the lens arraysubstrate 21.

FIG. 11A illustrates a luminescent panel 11′ in which the transparentsubstrate 2 of the luminescent panel 11 shown in FIG. 4A is substitutedby the lens array substrate 21. The anode electrode 3, the organic ELlayer 4 and the cathode electrode 5 are sequentially laminated on theflat surface 21 a of the lens array substrate 21. The corrugated surface21 b of the lens array substrate 21 is a light emitting surface, and aplurality of convex lenses 21 c are arranged in the matrix form. Theconvex lens 21 c has the same circular cone shape as that shown in FIG.9A. Furthermore, each convex lens 21 c is superimposed on the convexlens 72 c in such a manner that the apex of each convex lens 21 c isopposed to the small bottom surface of the truncated cone of the convexlens 72 c when seen from the plane surface. In FIG. 11B, a line L11′represents a light intensity ratio of the luminescent panel 11′illustrated in FIG. 11A, and this is expressed as a relative valuerepresenting the light intensity as 1 when viewing the luminescent panel901 from the normal line direction of the surface 902 b as a comparativeexample. Here, there is illustrated a case that the apex angle β of theconvex lens 21 c is 100°. The luminescent panel 11′ is brighter than theluminescent panel 901 over approximately 180°. In particular, itdemonstrates the brightness equal to or above the front face brightnessof the luminescent panel 901 over approximately 45° on the right andleft sides from the front face direction of the lens array substrate 21.

FIG. 12A shows a luminescent panel 12′ in which the transparentsubstrate 2 of the luminescent panel 12 depicted in FIG. 5A issubstituted by a lens array substrate 21. The anode electrode 3, theorganic EL layer 4 and the cathode electrode 5 are sequentiallylaminated on the flat surface 21 a of the lens array substrate 21. Onthe other hand, the corrugated surface 21 b of the lens array substrate21 is a light emitting surface, and a plurality of convex lenses 21 care arranged in the matrix form. The convex lens 21 c has a circularcone shape. Moreover, each convex lens 21 c is superimposed on theconvex lens 73 c in such a manner that the apex of each convex lens 21 cis opposed to a small bottom surface of the truncated cone of the convexlens 73 c when seen from the plane surface. In FIG. 12B, a line L12′represents a light intensity ratio of the luminescent panel 12′ shown inFIG. 12A, and this is expressed as a relative value representing thelight intensity as 1 when viewing the luminescent panel 901 from thenormal line direction of the surface 902 b. Here, there is illustrated acase that the apex angle β of the convex lens 21 c is 100°. Theluminescent panel 12′ is brighter than the luminescent panel 901 overapproximately 180°. In particular, it demonstrates the brightness equalto or above the front face brightness of the luminescent panel 901 overapproximately 45° on the right and left sides from the front facedirection of the lens array substrate 21.

FIG. 13A shows a luminescent panel 10″ in which the transparentsubstrate 2 of the luminescent panel 10 depicted in FIG. 3A issubstituted by the lens array 22. The anode electrode 3, the organic ELlayer 4 and the cathode electrode 5 are sequentially superimposed on theflat surface 22 a of the lens array 22. The corrugated surface 22 b ofthe lens array 22 is a light emitting surface, and a plurality of convexlenses 22 c arranged in the matrix form are formed by the corrugatedsurface 22 b. The convex lens 22 c has a circular cone shape. Inaddition, the convex lens 22 c is shifted from the convex lens 71 c by ahalf pitch in column and row directions. That is, the apex of eachconvex lens 22 c is opposed to a valley between the convex lenses 71 cand each valley between the convex lenses 22 c is opposed to the apex ofthe convex lens 71 c when seen from the plane surface. In FIG. 13B, aline L10″ represents a light intensity ratio of the luminescent panel10″ depicted in FIG. 13A, and this is expressed as a relative valuerepresenting the light intensity as 1 when viewing the luminescent panel901 from the normal line direction of the surface 902 b. Here, there areillustrated a case that the apex angle β of the convex lens 22 c and theapex angle α of the convex lens 71 c are 90° and a case that the apexangle β of the convex lens 21 c and the apex angle α of the convex lens71 c are 100°. The luminescent panel 10″ is brighter than theluminescent panel 901 over approximately 180° even if the both apexangles α and β are 90° or 100°. In particular, it demonstrates thebrightness equal to or above the front face brightness of theluminescent panel 901 over approximately 45° on the right and left sidesfrom the front face direction of the lens array 22.

Although the lens array may not be bonded to the cathode electrode 5,the lens array must be used rather than the transparent substrate inthis case. FIG. 14A shows an example of such a luminescent panel 16.

As shown in FIG. 14A, the anode electrode 3, the organic EL layer 4 andthe cathode electrode 51 are sequentially superimposed on the flatsurface 21 a of the lens array substrate 21. This cathode electrode 51is different from the cathode electrode 5 in that it does not have thetransmissivity with respect to the visible light but has thereflectivity. Therefore, the cathode electrode 5 acts with the mirrorsurface. On the other hand, the corrugated surface 21 b of the lensarray substrate 21 is a light emitting surface, and the convex lenses 21c are arranged in the matrix form. The convex lens 21 c has a circularcone shape. In FIG. 14B, a line L16 represents a light intensity ratioof the luminescent panel 16 of FIG. 14A, and this is expressed as arelative value representing the light intensity as 1 when viewing theluminescent panel 901 from the normal line direction of the surface 902b as a comparative example. Here, there are illustrated cases that theapex angle β of the convex lens 21 c is 90° and 100°, respectively. Theluminescent panel 12′ is brighter than the luminescent panel 901 overapproximately 180° even if the apex angle β is either 90° or 100°. Inparticular, it demonstrates the brightness equal to or above the frontface brightness of the luminescent panel 901 over approximately 30° onthe right and left sides from the front face direction of the lens arraysubstrate 21.

Although the concave mirror is formed by bonding the flat surface of thelens array having the reflecting film formed thereon to the cathodeelectrode in the foregoing embodiments, the present invention is notrestricted to the above embodiments as long as the concave mirror facesthe cathode electrode.

For example, in the luminescent panel 17 shown in FIG. 15, thereflecting film 8 is formed in such a manner that its outer surface(outer surface relative to the organic EL layer 4) is in contact withthe irregular surface 32 a of the opposed substrate 32. That is, sincethe shape of the reflecting film 8 can be formed in accordance with theshape of the irregular surface 32 a of the opposed substrate 32, thedirectivity of the reflected light on the reflecting film 8 can be setby setting the shape of the irregular surface 32 a of the opposedsubstrate 32. Additionally, spaces 31 are formed between the cathodeelectrode 5 and the reflecting film 8, an inert gas with a rowrefraction factor (e.g., a nitrogen gas, a helium gas, an argon gas, aneon gas and others) is filled in the spaces 31, thereby restrictingcorrosion of the cathode electrode 5 and the reflecting film 8.

As a method of manufacturing the luminescent panel 17, after forming thefilm of the anode electrode 3 on the flat surface 2 a of the transparentsubstrate 2, the transistor or the partition wall (not shown) is formedaccording to needs, and the anode electrode 3, the organic EL layer 4and the cathode electrode 5 are sequentially formed. Then, a concaveportion 32 c is formed on one surface of the opposed substrate 32 (theconcave portion 32 c is not formed at this moment) by thephotolithography step.

The reflecting film 8 is formed on the irregular surface 32 a of theopposed substrate 32 by the vapor deposition method or the like, thetransparent substrate 2 and the opposed substrate 32 are attached toeach other in such a manner that the reflecting film 8 is arranged onthe cathode electrode 5 side, thereby bringing the luminescent panel 17to completion. On the irregular surface 32 a, a plurality of the concaveportions 32 c are patterned in the mesh formed as seen from the planesurface, and the spaces 31 are arranged in the matrix form as seen fromthe plane surface. It is to be noted that a silhouette of the space 31has the same shape as a silhouette of the convex lens 7 c shown inFIG. 1. It is desirable that the reflecting film 8 is in contact withthe cathode electrode 5 in terms of the reflectivity or the contrastratio. However, when a plurality of stripe electrodes constituting thecathode electrode 5 are provided and signals applied to the respectivecathode electrode stripes are different from each other, it is desirableto interpose an insulating material so that the reflecting film 8 andthe cathode electrode stripes are electrically insulated from eachother. When the step of attaching the transparent substrate 2 and theopposed substrate 32 with each other is performed in the inert gasatmosphere, the space 31 has the inert gas atmosphere therein. Attachingthe opposed substrate 32 having the reflecting film 8 formed thereon tothe transparent substrate 2 forms concave mirrors facing the cathodeelectrode 5.

In regard to the luminescent panel 17, like reference numerals denoteconstituent elements equal to those in the luminescent panel 1.

The reflecting film 8 of the luminescent panel 17 may also function asthe cathode electrode. In this case, the film of the cathode electrode 5does not have to be formed on the organic EL layer 4. FIG. 16 shows aluminescent panel as such an example. As to the luminescent panel 18,like reference numerals denote constituent elements equal to those inthe luminescent panel 17. In the luminescent panel 18 shown in FIG. 16,the reflecting film 52 which reflects the visible light is formed on theirregular surface 32 a of the opposed substrate 32, the spaces 31 isformed between the organic EL layer 4 and the reflecting film 52. Thespace 31 has the inert gas atmosphere (e.g., a nitrogen gas, a heliumgas, an argon gas, a neon gas and others) therein. The reflecting film52 serves as concave mirrors in the spaces 31. Further, the reflectingfilm 52 is in contact with the organic EL layer 4 at the parts of theconcave portion 32 c of the opposed substrate 32 and also functions asthe cathode electrode. That is, the surface of the reflecting film 52which is in contact with the organic EL layer 4 is formed of a materialwith a relatively low work function.

As a method of manufacturing the luminescent panel 18, after forming thefilm of the anode electrode 3 on the flat surface 2 a of the transparentsubstrate 2, the transistor Tr or the partition wall 9 (not shown inFIG. 16) is formed according to needs, and the film of the organic ELlayer 4 is formed on the surface of the anode electrode 3.

On the other hand, the concave portions 32 c are formed on one surfaceof the opposed substrate 32 by the photolithography step.

Then, the above-described cathode electrode material is evaporated onthe irregular surface 32 a of the opposed substrate 32 in order to formthe reflecting film 52, and this opposed substrate 3 is attached to thetransparent substrate 2 so that the reflecting film 52 comes intocontact with the organic EL layer 4 to form the spaces 31, therebybringing the luminescent panel 18 to completion. When this step iscarried out in the inert gas atmosphere, the spaces 31 has the inert gasatmosphere therein.

The space 31 of the luminescent panel 18 may be filled with the organicEL layer 4. FIG. 17 shows a luminescent panel 19 as such an example. Asto the luminescent panel 19, like reference numerals denote constituentelements equal to those in the luminescent panel 18. In the luminescentpanel 19 shown in FIG. 17, the reflecting film 52 is formed on theirregular surface 32 a of the opposed substrate 32, and the organic ELlayer 4 is formed between the anode electrode 3 and the reflecting film52. Therefore, the reflecting film 52 has the concave shape with respectto the organic EL layer 4 and functions as concave mirrors. The organicEL layer 4 has a shape that the concave portions 33 corresponding to theconcave portions 32 c are continuous, and function as lenses withrespect to the light transmitted through the organic EL layer 4.Additionally, the reflecting film 52 also serves as the cathodeelectrode, and has a laminated structure consisting of a first layerwhich is in contact with the organic EL layer 4 and has a relatively lowwork function and a second layer which is thicker than the first layerand has a relatively high work function. Further, the reflecting film 52has the reflectivity with respect to the visible light.

The opposed substrate 32 of the luminescent panel 19 may not beprovided. FIG. 18 shows a luminescent panel 20 of such an example. As tothe luminescent panel 20, like reference numerals denote constituentelements equal to those in the luminescent panel 19.

As a method of manufacturing the luminescent panel 20, after forming theanode electrode 3 on the flat surface 2 a of the transparent substrate2, the film of the organic EL layer 4 is formed on the anode electrode3. Then, embossing the organic EL layer 4 provides a shape that theconcave portions 4 a of the organic EL layer 4 are arranged in thematrix form when seen from the plane surface. Further, forming thereflecting film 52 on the organic EL layer 4, the reflecting film 52functions as concave mirrors with respect to the organic EL layer 4.

In a luminescent panel 30 shown in FIG. 19, a transparent resin whichtransmits the visible light therethrough is filled in the space 31 inthe luminescent panel 17 depicted in FIG. 15. Although a method ofmanufacturing the luminescent panel 30 is substantially equal to themethod of manufacturing the luminescent panel 17, there is required astep of filling the transparent resin in the space 31 of the irregularsurface 32 a after forming the reflecting film 8 on the irregularsurface 32 a of the opposed substrate 32. Thereafter, when the irregularsurface 32 a having the transparent resin 34 filled therein is bonded tothe cathode electrode 5, the luminescent panel 30 is brought tocompletion. It is desirable for the transparent resin 34 to have arefraction factor substantially equal to that of the cathode electrode 5and also have a low transmissivity with respect to oxygen or water.

In a luminescent panel 19′ shown in FIG. 20, the transparent substrate 2of the luminescent panel 19 illustrated in FIG. 17 is substantiallysubstituted by a lens array 102, and a surface 102 a on which theorganic EL elements are to be formed is an irregular surface on whichconvex lenses 102 c are arranged in the matrix form whilst a surface 102b on the back side is flat. After patterning the anode electrode 3′ onthe surface 102 a, the organic EL layer 4′ and the cathode electrode 52which also functions as the reflecting film are appropriately formed. Atthis moment, the anode electrode 3′, the organic EL layer 4′ and thecathode electrode 52 are formed along the convex shapes of the convexlenses 102 c. A resin is applied to the surface of the cathode electrode52 by spin coating, thereby forming the opposed substrate 132 which alsofunctions as a sealing film.

In order to improve the luminescent brightness of the luminescent panel,the following structure may be adopted.

As shown in FIG. 21, a luminescent panel 40 has as a basic structure alaminated structure that a low-refraction factor material layer 43, theanode electrode 44, the organic EL layer 45 and the cathode electrode 46are sequentially laminated on one flat surface 42 a of the substantiallytabular transparent substrate 42.

The transparent substrate 42 has a transmissivity with respect to theinvisible light and an insulating property, and is formed of a materialsuch as a borosilicate glass, a quartz glass or any other glass. Arefraction factor of the transparent substrate 42 is approximately 1.5.

The film of the low-refraction factor material layer 43 is formed on oneflat surface 42 a of the transparent substrate 42. The low-refractionfactor material layer 43 has a transmissivity with respect to thevisible light, and a refraction factor of the low-refraction factormaterial layer 43 is smaller than that of the transparent substrate 42.Further, a film thickness of the low-refraction factor material layer 43is sufficiently longer than a wavelength of the visible light. As thelow-refraction factor material layer 43, a fluorocarbon resin isappropriate. There are, e.g., PTFE (refraction factor: 1.35), PFA(refraction factor: 1.35), PFEP (refraction factor: 1.34), MEXFLON-H15(refraction factor: 1.35, manufactured by Nippon Mektron, Ltd.), CYTOP(refraction factor: 1.34, manufactured by Asahi Glass Company) andothers.

The film of the anode electrode 44 is formed on the low-refractionfactor material layer 43. The anode electrode 44 has anelectroconductivity and a transmissivity with respect to the visiblelight. Furthermore, as the anode electrode 44, one which can efficientlyinject the electron holes into the organic EL layer 45 is preferable.The anode electrode 44 is formed of, e.g., an indium-tin-oxide (ITO), azinc-doped indium oxide (IZO), an indium oxide (In₂O₃), a tin oxide(SnO₂) or a zinc oxide (ZnO) and others. It is to be noted that, if theanode electrode 44 is formed of ITO, its refraction factor isapproximately 2.0, which is higher than a refraction factor of thelow-refraction factor material layer 43 and also higher than arefraction factor of the transparent substrate 42.

The film of the organic EL layer 45 is formed on the anode electrode 44.The organic EL layer 45 may have a three-layer structure consisting ofan electron hole transport layer, a narrow-sense luminescent layer andan electron transport layer superimposed on the anode layer 44 in thementioned order, or a two-layer structure consisting of the electronhole transport layer and the narrow-sense luminescent layer superimposedon the anode electrode 3, or a single layer structure consisting of thenarrow-sense luminescent layer, or a laminated structure that aninjection layer for electrons or electron holes is interposed betweenappropriate layers in such layer structures, or any other layerstructure.

That is, the organic EL layer 45 has a function to inject electron holesand electrons, a function to transport electron holes and electrons, anda function to generate excitons by re-combining of electron holes andelectrons to emit the light. Although the organic EL layer 45 contains aluminescent material (fluorescent material), the luminescent materialmay be based on a high-molecular material or a low-molecular material.

The film of the cathode electrode 46 is formed on the organic EL layer45. The cathode electrode 46 has a reflectivity with respect to thevisible light. Furthermore, it is desirable for the cathode electrode 46to have a relatively low work function.

As a method of manufacturing the luminescent panel 40, a fluorocarbonresin is applied on one flat surface 42 a of the transparent substrate42 and incineration is performed, thereby forming a low-refractionfactor material layer 43 having a film thickness of approximately 100μm. Thereafter, the film of the anode electrode 44 is formed on thelow-refraction factor material layer 43 at approximately 150° C. by aplasma ion plating method, and the film of the organic EL layer 45 isformed on the anode electrode 44. Then, the cathode electrode 46 isformed on the organic EL layer 45 by the vapor deposition method.

Comparing the luminescent panel 40 with a luminescent panel without thelow-refraction factor material layer 43, when various conditions (e.g.,a film thickness of each layer, a level of an application voltage, aluminescent area, a level of a passing current and others) are equal,the luminescent brightness of the luminescent panel 40 is approximately1.5-fold of the luminescent brightness of the luminescent panel withoutthe low-refraction factor material layer 43. That is because the lightis refracted when entering transparent substrate 42 from thelow-refraction factor material layer 43 by forming the film of thelow-refraction factor material layer 43, a quantity of the light whichhas approximated 90° with respect to the light emitting surface 42 b isincreased, and a quantity of the light totally reflected on the lightemitting surface 42 b is thereby decreased.

The low-refraction factor material layer 43 may be a material includingair gaps (e.g., silica aerogel: 90% of its cubic content is air gaps),or an ultraviolet curing resin material including air gaps. The materialincluding the air gap or the resin has a substantial refraction factorlower than a refraction factor of a bulk material, and also lower than arefraction factor of the transparent substrate 42.

The present invention is not restricted to the foregoing embodiments,and various improvements and changes in design may be carried outwithout departing from the scope of the invention.

For example, although there is provided a structure that the anodeelectrode, the organic EL layer and the cathode electrode aresequentially superimposed from the transparent substrate 2, thetransparent substrate 42, the lens array substrate 21 or the lens array22, there may be adopted a laminated structure that the cathodeelectrode (which has the transmissivity with respect to the visiblelight), the organic EL layer, and the anode electrode (which has thetransmissivity with respect to the visible light when it does notfunction as the reflecting film, and does not have the transmissivitywith respect to the visible light but the reflectivity when it alsofunctions as the reflecting film) are superimposed in the illustratedorder from the transparent substrate 2, the transparent substrate 42,the lens array substrate 21 or the lens array 22.

Moreover, although description has been given as to the case thatorganic EL element that the anode electrode, the organic EL layer andthe cathode electrode are superimposed in the mentioned order from thetransparent substrate 2, the transparent substrate 42, the lens arraysubstrate 21 or the lens array 22 is applied to the luminescent panel,it is possible to apply to the luminescent panel an inorganic EL elementthat a first electrode (which has the transmissivity with respect to thevisible light), an insulating film (which has the transmissivity withrespect to the visible light), an inorganic luminescent layer, aninsulating film (which has the transmissivity with respect to thevisible light) and a second electrode (which has the transmissivity withrespect to the visible light when it does not function as the reflectingfilm, and does not have the transmissivity with respect to the visiblelight but the reflectivity when it also functions as the reflectingfilm) are superimposed in the mentioned order from the transparentsubstrate 2, the transparent substrate 42, the lens array substrate 21or the lens array 22.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A luminescent panel comprising: a transparent substrate; a firsttransparent electrode provided on the transparent substrate; aluminescent layer provided on the first transparent electrode; a secondtransparent electrode provided on the luminescent layer, the firsttransparent electrode, the luminescent layer and the second transparentelectrode defining at least one pixel; and a reflecting film whichreflects light emitted from the luminescent layer through the secondtransparent electrode, such that the reflected light is outwardlyemitted from the transparent substrate; wherein an inner surface of thereflecting film defines a space, and the reflecting film has a shapesuch that the reflecting film controls a direction of the reflectedlight to condense the reflected light; and wherein the space is filledwith an inert gas.